A bad phonecall can often be perfectly polite and conversational when the actual call is proceeding. After hanging up, both parties will normally say a word or phrase which sums up their opinion of the other person, e.g. 'Clown', 'Crook', 'Conman' or other words beginning with C.
telephone would record this word - or phrase if one person went so far as to say 'Bunch of Clowns' for example, and send it to the other person. This would help people to work out the exact opinion they were held in, and whether or not the phonecall actually went well. Sometimes it can be hard to tell, as already mentioned.
The embarrassment of actually saying the word during the call would be eliminated, and it would be a social faux-pas to actually dial the other person up and say 'Did you just call me a clown?'.
This idea cannot fail to bring about world peace.